Telephone-exchange system.



E. E. CLE MENTL TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED SEPT-B. 1905 1,235,186. 7 Patented Ju1 31,1917.'

I SHEETS-SHEET l.

I H 3 Smwnro;

wih waou v E. E. CLEMENT.

TELEPHONE excmmse svs rem.

AF'PUCATIOP FILED SEPT. 8.1905; Patented J uly 31, 1917.

I.SHEETS--SHEET 2.

E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

Witnesses E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED SEPT. 8, I905.

Patented July 3l, 1917.

ISHEETS-SNEET 4.

E.- E. CLEMENT; 1 msqliouiexcumee SYSTEM.

AP'UCATION FILED SEPT. B. 1905. 1,235,186.

Patented July 31; 1917.

1 suQTs-suEET s QQQW MQN SAN wwma

awwntou wahuom {UNITED or A1 ES PATENT OFFI EDWARD E. CLEMENT, OFWASHINGTON. DISTRICT OF CDll-U'IVEIHIA. ASSIGNOR, BY MESNE ASSIGNMENTS,TO JAMES R, GARFIELD. TRUSTEE OF GLEV'ELAND, OHIO.

TELEPHONE-EXCHANGE SYSTEM.

Application filed September 8, 1905,

To all whom it may concern lie it known that il llowann it. Ci'i'nnnxr,a citizen of the l nited States. residing at \Vashington in the Districtof Columbia, hare invented a certain new and uselul linprorenient inlelephone-Exchange Systems, of which the :l ollowing is a specification,re l lino-circrdts n'orided with individual linesignal relays at thecentral ollice, eaeh eircnit connected to multiple contra-ts in a uniteher of SWitchcS which 1 shall ,hereinaftm" terin primary selectors. Whena line calls ii relay ac to raiac the potential of its test terminals inall of the switches to which it is .multipled. The switch-arms areconstantly rotated and the First arm which OIJL'TOUHUZIS a contact ofthe line calling stops, and hy ll'l'HlIlS of a solenoid which itcarrier; sticks a plug into anopeniug in the group of springsassociated, with the teat terminal. thereby perfornrirn; the sanieinnelions performed by an operator when she inserts an answering pluginto the jack of a ailing line. l lach primary selector switch forms thetern'iinal of a trunk. whose other end is coi'inected .to

what I shall tern'i a secondary selector switch."

which. is aiin'ilar in its'constriwtion and op- .lia'ation to theprin'iary selector switch, and

'(an'nzaii'is l'l'll'lltipll? terminals of operators(Zm'd-cirei'iits,the other terminals of. which are plugs or Jacks orsimilar mamiai Qnlttl'h inn; means.

It will he ohri ons without iiurtl'ier expla V nation that by thisarrangement any incoming 1all nu iistrilnlted to any cord circuit in theexchange. Assuming for i 'istance that we are (lcalii'ig with anexchange of 10,000 lines, in which-there are 100 operators; assume thateach ii'icoining lino" innltipled ten timee to the switches of as manySpecification of Letters Patent.

'latejnted Jril 31, 1917.

Serial No, 277,524.

trunks; and that each cord circuit is innit-i- 'pled the same number oftimes to as many trunk switches. A calling; line may he picked up by anyone of ten different primary selectors or trunk switches, and this inturn may pick up through its secondary selector any oneoi tencord-circuits, hence the line has accee'e to one-hundred cord-oilcuits,and it the distribution be such that the first group of trunks goes tothe first cord-circuits o'l all the positions, the second group oftrui'ilts-to the second L',(',i1'tl-(,lll'0llllS and so on, then theeallingline has a possibility of access to every operator in theexchange.

My circuits are so arranged that during conversation there is but oneadditional tap oil the talking cireuih or one-halt an additionalhridfae. Single supervision all that required by the ope "ators, thatwhich is commonly called the answeringsupervisory being used in thisease as a calling; signal. The calling suhscriher controls his ownii0l1- nection tillfil'llili'tlji', the called subscriber alone heingsubject to delay tluough failure of the operator to pri'nnptlydisconnect. The ell'cct of this, however is minimized by triving: thecalled euhaeriher control oi. his own. stnierrisoev signal, so that hecan at all times attract the attention of the operi'itoiu The switch Iemploy comin'iaeis a shaft constantly driven a fixed collar on the shaftand a switclnarm carried thereby pro'riderfl with a clutch h'y which itcan be coupled to and ui'iconplcd. From the shaft with great quickness.Around the shaft is a circularly arranged seriea of linemontacts aelipair of talking contacts having an associated test terminal controlled.by the line-relay. The switch-arm. consists of a tube litt l withspool-howls and containing a con'ipo. to core fitted to slide within it,the inner end iron and the outer end insulating material. The

'tnhe carries the wii'idingo constituting aeolenoid. and the whole isincloaed in a drawn metal shell of cyhndruad shape canened. at one endto ehp on over the spool-h I. I The tube is firmly secured at its innerend to a,

spool-head and extend ftn'wardly, passing through bnel'ied openil'igs inthe end of the shell and threaded outside of the eame to receive nutsholding in place spring lna'ninals,

which as the arm is rotated by the shaft sweep over the switch-contactsheretofore mentioned.

The specific form of selector switch briefly described above is notclaimed herein, as it constitutes a separate invention. The claims inthe present case will be directed to the system as such, in which thisspecific form of switch is incorporated for purposes of definition andnot of limitation.

My invention is illustrated in the accompanying drawings wherein,

Figure 1 is a diagram showing a subscribers station anda centralstation, also the trunk circuit and two selector switches.

Fig. 2 is a similar diagram showing a cordtwo stud terminals 11: and w"tothe inner circuit and a subscriber-s station with its central officeequipment. Flgs. 3 and 4 are a cross section and a plan view,I'QSPOClZDQly,

of one switch. Fig. 5 is a diagram showing 5" the distribution of linesand cords. v\

Figs. 6 and 7 are diagrams showing modified arrangements for thedistribution of lines and cords.

1 will first describe the selector switches and their mode of operationand then describe the circuits.

The selector switch shown in Figs. 3 and 4 sweeps over a continuous ring:0 The shaft in the present case is shown as driven by a belt'L and apulley L, but it will be understood that the driving means may be of anysuitable description. The several selectors are all driven by preferenceon or from the same shaft, so as to secure not only economy of power andtransmission but perfect uniformity in speeds of the selector arms whichmay sweep over multiples of the same line.

The primary selector mechanism is shown at X, in Fig. l, and comprises asleeve or collar m with a flange, mounted loosely on the shaft andresting on the collar w"'which is fastto the shaft. \Vithin and servingas a bearing for the flange of the collar :n" is a collar which is alsofast to the shaft. The movable collar w is fitted with a projectingtubular arm preferably of copper or. brass, which carries the windings wand wupon it and the combination core and plug on within it, the armbeing thus a solenoid with a plunger core. The windings are held v1nplace by the two spool-heads a? ()n the front spool-head w" are ends ofwhich are attached the terminals of thewmdmgs w and m, respectively.

Thesolenoid is protected by the drawn metal dust-proof shell m whichslides over the spool-heads and has two bushed openin gs to pass theterminals w and act To the threaded ends/of theterminals, projectingthrough the hushed openings, are fitted the contact springs w and 00,held in place by suitable nuts. 0n the plunger, and resting against theouter head of the magnet, Within the case, is a helical coiled spring mby which the plunger is normally kept retracted toward the shaft asshown in the The function of this plunger is two-fold. In the normal oridle condition of the parts it serves as a coupling or clutch to holdthe arm fast on the shaft, its end projecting into an opening or socketin the collar-:10 as indicated at w. \Vhen the arm is opposite a callingline terminal the plunger is thrown forward and its outer end enters thejack ring 90 the inner end atthe same time leaving the socket in thecollar, thus stopping the arm and simultaneously spreading the jacksprings to form the necessary connections.

The inner end of the plunger w is of soft iron with a hard tip ifnecessary. Its outer end is of insulating material such as hard wood orfiber. The winding of the magnet is double, consisting preferably ofterminal of the outer winding isconnected ;to the contact spring 1:,through the stud 11:, the other terminal of the coil is grounded. themagnet is connected to the contact spring in, through the stud w, theother terminal of the winding is also grounded. In this particular caseI have grounded the shaft itself for convenience so it is only necessaryto connect the two terminals of the coils which are to be grounded tothe sleeve of the solenoid. i

Of course these two windings of the solenoid may be put on the tube orsleeve in any desired fashion. The only requirement is that eitherwinding when energized shall be able to pull and hold in the core, (0

One terminal of the inner winding of The solenoid or arm, X, is the onewhich 1 Instead of having a double wound coil, it

is only necessary to havea single coil, the two terminals of which areconnectedlo the contact springs w and m.

Having thus briefly described the coilstruction and operation of theselecto arms or solenoids, we may take up the circuits by which they arecontrolled. lu Fig. 1, the subscribers station shownat .r' is equippedwith the apparatus usually found in common battery installations, the.n-incipal "duration.

wires from this station terminate in a, line relay M through thecontacts of acut-ol-l' relay N. \Vhen the relay N 1; energized the linewires 1 and 2 are coi'inected to tl1e'e.\;-

tensions 5 and (5, respectively, which ter- 1ninate in, multiplecontacts in the banks of the different selector switches of the linegroup. Each line is inultipled in a certain percentage of these selectorswitches and also to the multiple jacks in the switchboard panels infront of the operators. In

group of selector switches the arms are set radially aroituid the shaftso that each line through its n'uiltiple contacts, is swept over duringone revolution of the shaft as many times as there are switches in thegroup. Suppose for illustration there were ten switches and the shaftmade one revolution k signal lamp s and the solenoid L The per Second,then every one ofthe ten 1nu1 tiple contacts of a particular line in thebank Would'be. swept over once in the second. By this arrangement thetime in answering a call or picking out a line is of very short The backcontact m of the relay M is connected to the contact in the bank. of theswitch X and also inultipled'to contacts in the other switches of thesame group. The trunk wires 9 and 10 are con nected to the bus contactsw and 121*, respectively. These contacts are common to all of the linesprings in'the banlt, so that when the plunger of the'solenoid isoperated any line in the bank can be connected to the trunk wires 9 and10. The contact m of the bank is connected to a normally open contact fof the relay P". The trunk Wires- 9 and 10 tenninate in the relay Sthrough the normally closed contacts of the relay 1? which whenenergized connects the answering end of the trunk to the calling end.The trunk wires 15 and 16 of the calling end of. the trunk terminate atthe bus contactsm and a), respectively, of X. The con'nnon contact an isconnected to normally open contacts in the relays 1"" and- S The.individual contacts :1 and w terminate the cord-circuit shown in Fig.2.

i The cord-cirdtdts of the various operators are distributed among thevarions selector -.s witches X in the same manner as the linccircuits ofthe "arious subscribers are distributed among the selector switches Thedistribution \an be made follo The No. 1 cord-circuit of each of a.certain set of operators is rnultipled in the banks of a certainnul'nber of groups of secondary selector switches, and the number 2cordcircuitfor each of the same set of operators is n'iultipled in thebank of a different group of selector switches and so on, thusdistrib1t1ting the cord-circuits of each operator among a very largepercentage of subscribers. Dis-- ;tr1but1on similar to that in manualsystems can also be. had if desired, by connecting the cord-circuits ofeach operator to one group of selector switches, thus allowing a particu' lar (merator to attend to the wants of a certain class ofsulrscribers. The distribution can'be varied in any manner and anyparticular class distribution etl'ected. This illustrated in Fig. 5,which shows the first scheme, whereby the primary selector switches haveeach 100 line terminals, and; the sicondaryselectors e.- :h 10 cordtcrnn nals. Further reference-will be made to this hereaften 1het'crring now to Fig. 2, the answernig end of the cord-circuit hasrelay S and retardatimi coil I with bridged. battery be- I tween. themconnected to trunk wire 21 and 2:2 res 'iectively. The relay and coilfurnish talkingcurrei'rt for the calling subscriber, and the relay Scontrols tl1e,..circ1.1it of the calling and answering ends of the cordare separated by the condensers C and C. The calling end terminates inthe plug P, to the tip and sleeve of which are connected, re

spectirely, the bridged relays S and S the. bank of the selector switchX. at l also to 1ts inultlple contacts in the other switches of the samegroup by the following path: battery. B, 12, m, m, 13 to :r.- The firstsolenoid or arm in p 'ing around comes into eoiitact with the springstand beronies'energized by'currcnt flowing from. m thrt'mgh tlieioutorwinding it to ground. The sol u'i'ir-l'being thus ei'iergized theplunger m drawn forward, the insulated end enters a ring 1: and theother end leaves the notch a? in the collar :12, thus freeing the armfrom the revolving shaft X. The insulatcd end of the plunger enteringthe ring a closes the contact springs 11, rand :12,

1 4 thereby connect g the callnra line to the circuit of the innerwinding :12" by the fol..

lowing path: battery 13, 14:, 3, S, 7, 2:",

The solenoid X, being dew", m, :12 to ground. The relay S becameenergized when the trunk connection was effected by battery currentflowing through the contacts p and p of relay P over the sleeve side ofthe line No. 2 through the subscribers station and back over No. 1 sideof the line to No. 9 side of the trunk and through the contacts, [1 andp of the relay P to ground through S The calling subscriber is .nowconnected to an idle trunk, and the next step in order is to pick out anidle cord in front of an operatof who will then complete the connectact:0.

tion in the regular manner. It will be noticed that the solenoid X whilerotating is inactive, that is, the winding of the coil is open, oneterminal being connected to the normally open contacts of the relay S.This relay now being energized, the contacts s and s are closed and theterminal 12 of the coil is grounded and ready to pick out an idle cordin front of some operator.

Referring to Fig. 2 it will be noticed that .the contact x of the. bankis connected to battery through a normally closed contact of the'relay S-and in series with normally closed contacts 8'' and s of'the relay S.lVhen a cord is in use, that is, when it is inserted in' a jack therelay S is energized and the contact 8 is broken, disconnecting batteryfrom the'eontact w of the bank and making it impossible for a solenoidto operate on a busy cord. The foregoing circuit being in series withcontacts s and s of the relay S prevents more than one switch coming torest on the same coll L101 the relay S becomes energized immediately thecord is picked out, breaks apart the contacts 8 and s, and disconnectsbattery from the con This contingency has to be provided for because theoperator might not answer the call at once and the different switchessweeping around'snccessively would find battery on connected testcontacts, thereby tying up a number of them.

A ground now beim placed on one terminal of the winding 0? the solenoidand the other terminal connected to the test wiper or contact, theswitch is in condition torpick out an idle cord in front of one. of theoper- ]u. finding an idle cord, that is a test contact in the bankconnected to battery through the cord-circuit relays, the circuit of thesolenoid is completed by the following path: ground, 8, s, 17, (E26, .11:11, w, 01", m 11;,20, s, s 20, s, x, 31, to battery I). The plungerofthe solenoid now springing forward closes the contacts :11, w and w,w, connecting the trunk wires 15 and 16, resl'iectively, to the, wires21 and 22 of the cord-circuit, Fig. 2. The instant this connection takesplace, the circuit of the relay 1 is closed by the following path:battery B, 27, I, 24, 22, w, m, 16, 17, to ground. This relay nowbecoming enerby the following path: battery 13, 18,

gized attracts its armatures and connects the wires 9 and 10 to thewires 15 and 16 respectively thus completing the circuit from thecalling subscriber to an idle cord. .After this circuit is completed therelay S becomes energized by battery from the coil I through -the sleeveside of the trunk to the calling winding on the solenoid. Now in placeof this ground, battery is connected direct through contacts, p and 3/of the relay P and at the same time battery is disconnected from theother terminal of, the winding through the contacts of the relay S andground connected in its place. The circuit of the winding on thesolenoid is now closed r, 19, 17, 0 m at, 50 cf, 11;, as 20, s, s,25,'to ground, thebattery connection simply being reversed. The solenoidX in. place of being kept energized by the relay S is held so by therelay P" by the following path: battery B, 18, p 3/, 7, 2;, m", a, w, toground. v

Referring again to Fig; 2 the relay S becoming energized closes thecircuit of the signal. lamp 8' by the following path: ground 25, a, 28,.e'", 26. M .5, 31, to battery B. The operator noticing the lamp glowinguses her listening key and asks the number of the line: desired. Placingthe plug 1 into the jack .l of thedesired line she rings "in' theordinary manner. This'insertion connects the relays N and S in series,the relay N attracting its armatures disconnects the line relay M andconnects the calling line to the springs j and j of the jack J. Therelay S becoming energized opens the contacts s" and s extinguishing thelamp 8 and at the same time closing thecircuit ot the lamp W whichcontinues to glow until the called subscriber answers. Upon answering hecloses the line circuit and energizes the relay i. i tying the operatorthat he has responded.

The reason for reversing battery through the winding on the solenoid X,was to remove battery from the test contact .11 and so render it busypreventing other switches from stoppin At the end of the conversationthe calling, sul'iseriber hanging up, the relay S becomes.

deenergized and ground is removed from the test contact :r and batteryconnected instead. and as battery is also connected to the otherternnnalof X it becomes dei in- "ergized and the plunger returning to its normalposltion under the tension ofthe spring disconnects the trunk wires 15and 'lli-res wctlvely from the rord-circuit wires 21 and -Asssoonasthlshappens the extinguishing the lamp 8, noif' tics of i all theapparatus returns a uitidlc l')y.pl

Jrelay l hecomes dci nergized and opens the contacts p and. p. releasingthe solenoid/X .which. upon returning to its normal,positi u under theinl'lucuce of the spring .c "':"dis ;'(3(')1'1l'1t!tfth' the callingline froin the. trunk and its norjual or starting" position. the armslland, again contirming to rotati as heforc. "[hc called suhscriher inhanging up dccucrgized the relay S which again closes the circuitof thelamp 5 which upon glowing the. second time notifies the operator thatthe conversation is finished, \YllEIQl'lPUIl she withdraws the plug rending that particular cord-ciracing battery on the test contact again.

From the tm'egoing description it will he ru'iticetl that the callingsuhscriher has absolute control over his connection. at all times, andin case of a recall he simply hangs up and automatically disconnectshimself from. the cord'circuit and in taking down his telephone again heis auti'nmitically connected to al'n'itlier cord-circuit.

l'tclerrii'ig to Fig. 5, out one schei'uc of (list ution of the linesand cord circuits to the primary and secondary selectors.Thearrangement. is supposed to he applied (rairexchangc of 10,000Hlllltlt"l'il]tl'$ and 1.0% of the lines, selectors, truulv's. and plugcircuits, arerepresented in the figure. The total number of trunks forthe wlu le 10,000 liner, assuming 10% as the pro 'ier proportion ofconnective circuits to have therein laid he pri'n'ided, is 1000, eachtrunk having at the line end a primary selector X and at theswitchlalard. end a secondary selector X. Ilach primary selector switchcontains ill!) line terminals. while each secondary selcctor containsltl-cord terminals. Each line and each cord has 10 multiples and Idivide all the selector switches with their trunks into gri'iups of 10.I may tl'ierefore call this verv appropriately a. decimal trillution.,lt to he distinctly understood l'mwever that I do not limit myself tothe aiiticular numhers l'iere set forth. I am quite well aware that inmost excl'ianges the .ell'icicncv of tl'l'll'llx'S is proportional,roughly spimlv'inir, to the size of their groups, onto the scope ofselection. In many cases with 10 trunhs in a group each trunk will carrycalls per day; with fill trunks in a, group each truuh WiIl carry lilt)or more calls per dav. I ha shown It) as a convenient multiplicr:

distrillution so tar as the operators are i'roucernial and their cordcircuits", but the cllicicncy of the trunks hetween the ktlfll tors willvary somewhat with the numl' in line multiples. or the nmnhcr ol'trunlfsl in a and the cure for any congestion llicicncy is simply toincrease the selector switches in a of line group, drop in e lllllllllllol trunks and v griiiup and consmpicntly the mimber multiples for thatgroup.

scheme of dis andl have climinatml the intapialh of I ITIBI'B comes inthe flexibility 0t tl'ie'system, whereby any condition can he met.

In the left of Fig. 5 .I have shown the iiidiridual trunks of the firstgroup, X, to which are connected lines From 1 to 100. In the right ofthe figure l have shown 9 lines, 1) pairs of selectors and J trunks,each sym-v holiy ing an entire group, and each so marlv'cd.

'l'he linc l--2 shown connected to the first group of primary selectors,and null- .tiplcd to the contacts 10, 20, 30, +0, etc., of therespective switches of that groin). It 'will he observed that the switcharms of the group are-all set around at different angles, so that theywill sweep over the corresponih ing contacts insuccession.since allthearms are lacing constantly rotated at the same, speed liy the sameshaft. It is apparent that the line 'l--i orauy li nc calling in thefirst .group of UN) lines may he picked up by any one of the primaryselectors X and so put onto the corresponding one of the trunks.

The arrangement of the cord circuits with regard to the secondaryselectors is as follows. 'lhe first group of lines. with which I am atpresent dealing, I have determined to distrilnite among the variousoperators, of whom there are 100 in the exchange, using for that purposethe number one plug and cord circuit of each opcratolz. In other wordscalls over nul'nher one group of lines are ahsorhed hy the number onecord circuits along the hoard. I' do not mean by this that all thenun'iher one cord circuits are taken up hy the first group o'l' lilies.On the col'itrary, there are 100' of these. numher one cord circuits,one for each )osition, and these will take care of 1000 lines, or 10groups. and these are precisely the 10 groups I have shown in Fig.5. Atthe hottom ol' this figure there are shown 10 plugs, each with. thecm-d-circaiit 2l--29 extending up to one of thesecondary selectorswitches X in the first group. aiul each multi 'lled to a seconrilaryselector in cycryouc ot' the other groups on the right, the multipleconnections laing nun-lied 21d. Each of the '10 plugs is symlmlic ot' a.grou not' 10, just as each ot'itln! lines. trunks and selectors 1n theright of the figure is symlmlic of a group otlt). Nlow suppose the linelj. is calling, and the ifirst three primary selectors are already busy.The. switch-armof the fourth selector in due course reaches the contactof the calling line and stops thereon as we have previouslydctcrmii'ied. This puts the The arm of the secondary selector will stopthen on the terminal of the cord 2122 leading tothe number l plug onposition number Thus it will be perceived that this line by the doubledistribution, first to a certain trunk and then to a certain cordcircuit, has reached an arbitrary position on the switchboard whichbears no apparent relation to its number whatever, similarly'byfollowing through the different ri mary and secondary selectors, we willnd it sometimes on the first section and sometimes on the last positionof the board. Any line from No. l to No. 1000 gets this samedistribution on the No. l plugs, and since we are dealing with lines inblocks of 1000, it would seem that averages would hold andsufficientfiexibility would be attained to prevent any but a negligiblenumber of lost calls.

Having thus described the principal scheme, I should point out one ortwo modifications which are almost obvious and whose importance demandsthat they be not for- It should be observed first that in-' gotten.stead of carrying the lilies in groups, the first group of 100 linesmultipled to the first group of 10 primary selectors, and thenmultipling the groups of plugs to the various groups of secondaryselectors, I can reverse this. That is, I can. multiple each line 10timesto as many switches of diiferent groups, such as. X-l0, X X ",etc.,

- and each group of plugs can. then be mul- -Fig. 6.

thereof which I now considerthe best, and

having also pointed out some modifications which are possible, 1' wishto state in closing that I am aware many other modifications and changescan be made without departing from the spiritof thc invention. All suchI consider within the scope and. purview 'hereof.

Among such changes are those in the nature of the drive of the shaft,which need not be constantly driven. Various'devices of clutches orelectrical motors with circuit controllers and the like can be used, butas these'are;.well understood in the art, I do not consider it necessaryto illustrate or further describe them. The effect of havin the motormechanism normally idle, so that swcring multiples of the lines,connective.

units, secondary selector switches containing multiples of the circuitsof the said connective units, and trunk lines connecting the primary andsecondary selector switches in pairs, each pair of switches constitutingan initial link between a calling line and the actual connectiveapparatus in the exchange, and each pair adapted to complete itsfunction in response to a call, by connecting the calling line to anidle unit, before the performance of any act to select the wantedsubscriber, substantially as described.

2. In a telephone exchange system, means for distributing callscomprising primary selector switches divided into groups, a group ofline-circu its multipled to terminal contacts in aach correspondinggroup of primary selectors, connected units, secondary selectorsconnected to the prilnary selectors, and multiple terminals in saidsecondary selectors for the connective units, each pair of primary andsecondary selector switches adapted to complete its function ofconnecting a calling line to an idle connective unit as a preliminary tothe-selection of the wanted subscriber, substantially as described.

3. In a telephone exchange system, means for distributing callscomprising automatic primary and secondary selector switches,line-terminals in the former, and connective-w circuit terminals in thelatter, a switching member for each primary selector switch with anelectromagnet to actuate thesame and means controlled by the callingline to energize said magnet, together with a switchin g member for eachsecondary selector with a controlling electromagnet, means to energizesaid controlling electromagnet through said primary selector andadditional energizing means for said controlling. electromagnetincluding connective circuit terminals of said secondary switch.

4a. In a telephone exchange system, means for distributing callscomprising automatic primary and secondary selector switches,line-terminals in the former, and connectivecircuit terminals in thelatter, a switching member for each primary selector switch with anelectromagnet to actuate the same means controlled by the calling lineto energize said magnet, together with a switchi ng member for eachsecondary selector with a controlling eleetromagnet, means to ener-'gize said controlling electromagnet controlled by thc operation of theprimary selector, and additional energizing means for said controllingelectromagnet including terminals of connective circuits which are notin use, substantially as described.

5. In a telephone exchange system, a sub scribers station and a metalliccireuitcxtending therefrom to a central station, connective units at thecentral station, an individual relay and battery connections for theline. at the central station, a primary selector switch containingtalking circuit terminals and testing means tor the line, saidline-relay controlling the condition ofthe said testing means. asecondary selector switch connected to the primary selector andontaining multiple talking circuit terminals and testing means for theconnectiyeunits, and means for actuating both primary and secondaryselector switches, said means also controlled initially by theindividual relay of the calling line. whereby the switches willautonuitically establish connection from the. line to an idle connectiveunit. substantially as described.

t'. in a telephone exchange system, a plurality ot' line-circuits and aplurality otlinkcircuits for interconnecting the lines, togetherwithintermediate means for distributing the calls among and uniting tllulines when calling to the liulccircuits, comprising the followinginstrlnuentalities: a primary selector switch containing line-terminalsand test terminals theret'or, a secondar selector switch containinglink-circuit terminals aml test terminals therelor, a. controllingmagnet tor eaelr switch energized through the test terminals. a linerelay and source ot' current' for each line energized. in response to acall to change the condition ot'its test terminal in the primaryselector switch to thereby put the same in connection with the callingline. a relay associated with the pri- ..mary selector and acting uponopcratit'm of the latter to render operative the circuit oi thecontrolling magnet ot the secondary se,- leetor, a relay associated witheach link-circuitadapted to change the condition of its test terminalamt to operatesaid secondary selector when the linlt is idle, and meanswhereby at'ter connection between two subscribers is completed, thecalling subscriber may control the circuits of both selectors,substantially as described.

7- ln a' telephone exchange. system, a seloctor switch normallydisconnected from the, lines, means to connect the same so as to f rmthe terminal of a calling subscribefs line. and a. plurality oflinl\'-circuit.s having terminals in said switch, a controlling magnet,for the switch and a pair of relays for each link jointly controllingthe condition of the test terminal thereof, one of said relaysresponding to current in the calling end of' the circuit only, and theother relay controlled by an operator in the use of the linkcircuit.substantially as described.

S. In a telephone exchange system, a subscriber's metallic line-circuitand multiple connection terminals therefor at a central otlice. normallydisconnected from the line,

certain of said terminals being spring-jacks for manual connection, andan automatic switch containing one or more of the other terminals.together" with a cut-off relay adapted when energized to connect theline to the terminals, means controlled through the automatic switch orthe jacks to 'enerwith stationary trunk contacts, cordcircuitcon'tactsfand solenoid control contacts. a

common source of current, and means for effecting the intereonuection ofthe line circuits through said trunk and cord circuits by means of saidprimary and secondary selector switches. i

it), In atelephone exchange'systenr a pin rality of subscribers lines, anumber of'operators circuits less than the number of lines. and selectorswitches containing m ni tiple contacts of both the. lines and theopcraters circuits. together with means associated with saidswitehes'and responsive to currentchanges in calling subscribers linesadapted to automatically connect the same with idle operat rs circuits.

11. in a telephone exchange system, a

plurality of subscribers lines. an operator's circuit, a calling signalassociated with said eircuil and an automatic switchingfiapparatusnorinally disconnectul but'eontaining a terminal of each line and ot'the operators circuits. and responsive to currentelntnge in a callingline to connect the same to the operators circuit. and to display thc-.operators signal. substantially as described.

12. In a teleplu'me exchange system, a ,plur;alit\' ol' subscriberslines, operators cir" cuits less in number than the number of lines.-acalling signal for each.operators circuit, and automatic switchingapparatus containing terminals of the lines and also containingterminals of the opc'ators? circuits, said switching apparatus adaptedwhen a line is calling to autoimltieal-ly select. and connect said lineand an idle operator-s i -=in both the lines and the link cirucits,means circuit, at the same time displaying the associated callingsignal, substantia ly as described.

13; In a telephone exchange system, a plurality of line circuits, anumber of linkcircults less than the number of lines adapted tointerconnect the same for conversation, at number of operators callingsignals also less than "the n'lunber of lines, automatic switch ing apliaratus containing multiple terminals responsive to current change in acalling line for causing the switching apparatus to select said line andalso to select an idle operators signal. and an idle link" circuit, andmeans whereby the operator may communicate with the callmg subscriberand manually com .plete the connection desired, substantially asdescribed.

14-. A telephone system including telephone lines, manually controlledoperators connecting apparatus and a link-circuit having automaticallycontrolled active terminals at one end to select the line and similarterminals at the other end to select. the connecting apparatus.

15. A telephone system including a plurality of telephone lines, a lessplurality of operators signals at the exchange and a linkcircuit havingautomatically controlled ac tive terminals at either end to respectivelyselect the calling line and select and display jone of said signals.

phone lines 111 character, mechanism operative when a subscriberinitiates a call to render the terphone lines, manually controlledoperators connecting'mcans, and selector switches connected in pairs,one switch of a pair being adapted to select the calling line and theother to select the first idle connecting means.

19. A telephone system including tele phone lines, multiple spring-jacksfor said lines at the exchange, operators cords for connecting with saidspring-jacks, call sig nals associated with said cord-circuits, andselector switches connected. in pairs, one switch of a pair beingadapted to select the calling line and the other idle cord and displayits signal.

-20. A telephone system comprising a group of telephone lines, a groupof operators connecting apparatus for inter-com necting said lines andan intermediate linkcircuit provided with. automatically controlledmechanism for interchangeably connecting one end of said link with. thelines of the group and the other end interchangeably with the connectingapparatus of the group. In testimony whereof I have ailixed my signaturein presence of two witnesses.

I EDWARD E. CLEMENT. Witnesses:

E. EnMoNsToN, Jr., C. A. STANOLIFF.

to select the first

